Pope Pius X promulgates Vehementer Nos, a papal encyclical condemning church/state separation. Pius issues this condemnation because of a 1905 French law separating church and state. The idea that government should be separated from ecclesiastical authority is denounced by Pope Pius X as "a thesis absolutely false, a most pernicious error".

According to Pope Pius X:

"The enemies of religion have succeeded at last in effecting by violence what they have long desired, in defiance of your rights as a Catholic nation and of the wishes of all who think rightly. ...

...it is in the first place guilty of a great injustice to God; for the Creator of man is also the Founder of human societies, and preserves their existence as He preserves our own. We owe Him, therefore, not only a private cult, but a public and social worship to honor Him. Besides, this thesis is an obvious negation of the supernatural order."

Pius also quotes Pope Leo XIII:

"Human societies cannot, without becoming criminal, act as if God did not exist or refuse to concern themselves with religion, as though it were something foreign to them, or of no purpose to them... "